As everyone knows a great many pipelines running along the bottom of the sea are likely to have to undergo repairs because of damage of various kinds suffered by them, as for instance, cutting by anchors, the leaking of fluid from inside the lines because of welding flaws, and also due to damage caused by a lack of cathodic or anti-corrosion protection.
Those well versed in the state of this art also know that much has been done towards achieving a system to deal with the repair of undersea lines in a way sufficiently efficient to meet the requirements of well-known operators and concerns working in this field. Among the systems known and in development at present one might briefly refer to, a) the "CAMERON" system, which makes use of a mechanical connector, cold forged at a pressure of about 1400 kg/cm.sup.2. It is used with some aid from divers or remotely operated vehicles, acting only upon the pipe to be repaired, spreading it into the coupling grooves and aligning itself with the pipeline, and when the connection is fixed onto the pipeline it also gives rise to a metal structure base which acts as a guide in the remedying of any fresh stretch of pipe. This system might become part of a wider repair system; b) the "SNAM" system which is an all-encompassing undersea pipeline repair system provided with accessories meant to clean, cut, and align the pipeline with the aid of ROV's and boat fitted with DP. It makes use of a cold forging system along with deformation of pipe and connector, namely a mechanical action, without use of any elastomers, in which deformation takes place in both parts to be joined. That is, the pipe is expanded into the connector, which also expands, but the connector material tries to return to its former state more strongly than does the pipe, and adds to the effect of such action, because of the different properties of the two metals. This makes this system seal better than does the CAMERON forged connector system, since several interference grooves come into being, thereby increasing interaction of the bodies concerned, such a system is disclosed in U.S. Pat. No. 4,648,626 of Mar. 10, 1987; c) the "ALSTHOM" fully designed system, provided with accessories to cut and clean both inside and outside, to remove concrete and casing. It employs a mechanical connector, only the end of pipe being cold forged, where a collar so formed provides the metal to metal seal with the connector. It makes use of amore complicated and less reliable forging process in terms of average and long term life than for the CAMERON and SNAM systems previously referred to; d) the "HYDROTEC" system, which makes use of Atmospheric Diving System (ADS) diving gear; which belongs to "Oceaneering". The system employs mechanical connectors adjusted with the aid of a manipulator--BMF (Bottom Manipulating Frame); e) the "ELF EQUITAINE" system is one that is part of and further to the "ALSTHOM" system referred to above. Mechanical connectors are used and they are laid on pipes that have had cold forging treatment; and f) the "IRDS" (International Robotics Diving Systems) system which uses the undersea pipeline aligning and repair supporting THOR system. The THOR system has many accessories that make it quite a practical system, and the connector and/or repairs are done by TIG orbital welding, which requires the aid of divers.
From the foregoing present trend is to ever-increasing use mechanical connectors, which are able to remedy evaluations, take up misalignments, and even be reused if wanted. Against such technique there is the fact that certain kinds of connectors employ gaskets and/or elastomers for sealing purposes, which are likely to age and even to leak after some time.
Furthermore, in spite of hyperbaric welding having been used for the great number of undersea pipeline repairs up to now, it is of general opinion, that repairs carried out with this technique, in addition to being complicated because of the safety of the men engaged in such work, also seriouly curbs any automation of the process, because of the environmental factors that directly affect the quality and the final result of the repairs done. It is generally acknowledged that repairs that follow this technique are hardly feasible in deep waters without the aid of divers (400 m), which means that repairs done with mechanical connectors are to be preferred in deep waters, since they are more easily automated.